The main mission of our core is to assist NIH scientists in generating genetically engineered animal models to support their scientific research. Genome engineering technologies have been advancing very rapidly in the past decade, especially the so-called CRISPR (clustered regularly interspaced short palindromic repeat) method has dramatically changed the way animal models are created. In the past several years, our core has spent a significant portion of our efforts on keeping up with the latest technological developments and efficiently applying them to animal model generation. We have been collaborating with Dr. Lothar Hennighausens laboratory on developing capabilities for using base-editors, a latest variant of CRISPR technology, to generate knockin mouse lines, and using whole genome sequencing approaches to analyze on-target and off-target mutations caused by various base-editors as well as the conventional CRISPR/Cas9 method. We have also successfully used Cpf1, an alternative enzyme to Cas9, to generate mouse models. Besides developing capabilities in using the latest CRISPR technology, we have been continuingly using the classical genetic engineering, embryonic stem cell, and assisted reproductive technologies to provide a range of services, including generating transgenic mice and chimeric mice, re-deriving mouse lines, resurrecting mouse lines using in vitro fertilization, and assessing stem cell differentiation propensities through teratoma formation assay. Overall, these collaborations and technical services have led to over 20 co-authored publications. In addition, Dr. Yubin Du, a biologist working in our core, and I have co-edited a volume of Methods in Molecular Biology, which consisted 30 chapters of modern methods related to animal model development.